1. Field of the Invention
The present invention relates to a method of selectively forming semiconductor devices such as a semiconductor laser (a laser diode) and a field effect transistor on a substrate, and an apparatus therefor and, more particularly, to integration of these semiconductor devices.
2. Description of the Prior Art
As a conventional method of integrating semiconductor devices having different characteristics on the surface of a substrate, the following techniques of performing crystal growth once, then patterning in the atmosphere, and crystal growth again are known.
One technique of integrating a two-wavelength laser structure is described in Applied Physics Letters, Vol. 58, No. 23, 10 Jun. 1991, pp. 2,698-2,700. According to this technique, a GaAs laser structure having an emission wavelength of 0.85 .mu.m is formed by Molecular Beam Epitaxy (to be referred to as MBE hereinafter), this laser structure is removed by patterning to form stripes at a pitch of 250 .mu.m, and an InGaAs laser structure having an emission wavelength of 1.0 .mu.m is grown again by MBE.
Another technique related to a vertical cavity-type laser is described in Japanese Journal of Applied Physics, Vol. 32 (1993), pp. 600-603. In this technique, one vertical cavity is grown by MBE, and the cavity is removed by patterning to form stripes at a pitch of 125 to 250 .mu.m. Then, a vertical cavity is grown again by MBE to integrate a laser structure of the single cavity and a detector of the double cavity.
In any one of the above two conventional techniques, however, a grown substrate is unloaded into the outer atmosphere after performing crystal growth once in a high vacuum, and patterning is performed on the substrate. Thereafter, crystal growth must be performed on the resultant substrate again in a high vacuum in the growth chamber. These steps complicate the process. In addition, these steps cause degradation in quality of the regrown crystal and formation of a depletion layer at an interface. For this reason, the device characteristics may be inferior to those of a device formed by consistent growth in a vacuum.